This invention relates generally to the use of new excimer laser procedure designed to correct low to high myopia and, in particular, a method of using algorithm-driven lasers to correct vision by performing multipass ablations, multizone ablations or a combination thereof.
Previous studies performed in different centers suggest that standard PRK for low myopia predictable with few complications. Contrastingly, results in myopia higher than -6 D are more unpredictable due to regression of effect often accompanied by scar formation. Because the quality of the ablation is an important factor in the final visual outcome, one of the first attempts to improve post-operative visual acuity was to limit ablation depth by using multizone techniques. However, there is no change in the degree of haze or in regression when using the technique.
To circumvent the amount of correction allowed by some laser software programs. PRK was performed in a series of steps. For example, a two-step procedure or a multi-step PRK was tried with little haze formation. A different approach involves a second ablation, created outside of the initial, standard PRK ablation, produced a transition zone. This procedure resulted in less regression, but the healing process took longer.
Although regression was lessened, results in eyes above -10 D were so discouraging that intrastromal PRK or laser assisted in situ keratomileusis (LASIK) have been suggested instead of superficial PRK in these patients.